1. Field of the Invention
The present invention generally relates to integrated circuits and more specifically to an insulator that simultaneously dissipates heat from high power devices using a high K insulator material and accommodates the low electrical permitivity/resistance needs of low power logic devices using a low K insulator material.
2. Description of the Related Art
With the advent of high performance/low power integrated circuit devices, low K dielectrics are commonly used to insulate the devices from adjacent substrates. Low K dielectrics offer reduced electrical permitivity and reduced thermal resistance when compared to high K dielectrics. While such electrical characteristics are very beneficial to low-power devices (such as critical paths, logic chains and other core logic devices), the low K dielectrics do not offer the high thermal conductivity which is required by high-power devices, such as electrostatic discharge (ESD) devices, clock buffers, and input/output (I/O) drivers.
Therefore, the integrated circuit designer must balance the electrical needs of the low-power devices against the thermal needs of the high power devices. This compromise reduces the performance of the low-powered devices and constrains the amount of heat which can be generated by the high-power devices. The invention described below eliminates this tradeoff and allows the integrated circuit designer to improve the performance of the low-powered devices and, at the same time, allows the high-powered devices to generate additional heat. Thus, the invention overcomes self heating of ESD structures, interconnects and circuits.
It is, therefore, an object of the present invention to provide an integrated circuit wafer that includes a substrate having first and second portions, a first insulator over the first portion, a second insulator over the second portion (wherein the first insulator has different thermal dissipation characteristics than the second insulator), and a silicon film over the first insulator and the second insulator.
The first insulator has higher thermal dissipation than the second insulator and the first insulator has a higher dielectric constant than the second insulator. The substrate includes first devices over the first insulator and second devices over the second insulator. The first devices generate more heat than the second devices, and the second devices require higher electrical permitivity than the first devices.
The first insulator and the second insulator could be adjacent one another and form a single planar surface upon which the silicon film is positioned. Alternatively, the first insulator could be positioned within the second insulator, adjacent the silicon film or the first insulator could be positioned within the second insulator, adjacent the substrate.
The invention also includes a method of forming an integrated circuit wafer that comprises forming a substrate having first and second portions, depositing a first insulator over the substrate, patterning the first insulator such that the first insulator remains only over the first portion, depositing a second insulator over substrate (the first insulator has different thermal dissipation characteristics than the second insulator), polishing the second insulator to form a planar surface, and attaching a silicon film over the first insulator and the second insulator.